This invention relates to a method of making molded articles containing a plurality of dissimilar fluid components in a predetermined spatial, non-laminate configuration. More particularly, this invention relates to a method of making such molded articles using a thin plate flow distributor to produce the predetermined spatial, non-laminate configuration.
Molded articles, in particular, those formed from plastic materials, have become a staple of domestic and industrial use. Plastics are particularly lightweight, replacing metal, glass, wood, and ceramics in numerous applications. Importantly, plastics can be water resistant, solvent resistant, weather resistant, etc., or can be composited to increase strength, flexibility, etc.
It is often desirable to impart to a molded product diverse properties or color. To achieve such diverse properties in one product frequently requires the product to be composed of two or more mutually dissimilar components each providing a desired property. Such products are often most efficiently made by coextruding multiple polymer streams into films or profile extrusions, or molding parts with more than one polymer component in the mold.
Conventional methods for accomplishing the delivery of multiple polymer streams to a common mold or extrusion port require complex machined parts which are usually quite bulky and expensive. Because of the design complexity characteristic of these conventional methods, there are often serious constraints on the ways in which polymer streams can be brought together. Furthermore, because distribution channels in flow distributors are generally machined to exhibit a predetermined configuration that is optimized for compatibility with the flow characteristics of the particular polymers flowing therethrough, a particular flow distributor can only be used in a particular method because the flow distributor has been designed for use with the particular polymers used therein.
Plate-containing flow distributors also have drawbacks. Typically, the distribution plates in such flow distributors are relatively expensive, thick metal plates which must be accurately drilled, reamed or otherwise machined at considerable expense. Moreover, with use, polymer material tends to solidify and collect in the distribution flow passages which must be periodically cleaned and then inspected to ensure that the cleaning process has effectively removed all of the collected material. The small size of the flow passages renders the inspection process tedious and time-consuming and, therefore, imparts a considerable cost to the overall cleaning/inspection process. The high initial cost of the distribution plates precludes discarding or disposing of the plates as an alternative to cleaning.
Multilayered articles and methods of making them are disclosed, for example, in U.S. Pat. Nos. 5,223,276; 3,773,882; 3,924,990; and 3,884,606. In U.S. Pat. No. 5,223,276, a multilayer film or sheet of diverse thermoplastic materials is made in a coextrusion apparatus composed of a slit die and a feedblock assembly containing a removable feedblock and a plurality of slotted, layer distribution passages which are mutually spaced apart and lie parallel to the slotted outlet of the die. U.S. Pat. No. 3,773,882 teaches a multilayer film coextrusion method wherein separate streams of two or more diverse thermoplastic materials are passed through a combining means containing a plurality of passages in which the streams are divided, interdigitated and discharged to form a composite layered stream which is parallel to a die orifice through which the stream is subsequently extruded to form a film. U.S. Pat. No. 3,924,990 discloses a coextrusion apparatus for making laminates of two or more diverse thermoplastic materials, wherein the apparatus is made up of a sheeting die and a distribution manifold containing a replaceable distributor block composed of a plurality of passages. In U.S. Pat. No. 3,884,606 , a multilayer coextrusion method is disclosed which involves dividing and re-combining first and second streams of diverse thermoplastic material in a stream dividing means composed of a plurality of passages to form a composite stream which is then extruded.
Each of the patents discussed above teaches a method and apparatus for making multilayer articles, specifically interdigitated (i.e., containing alternate layers of the diverse materials) multilayer articles. Although multilayer articles are continually desirable, the above patents are limited to forming film laminates and do not suggest molding non-laminate articles composed of two or more diverse materials in a predetermined spatial, non-laminate configuration.
It would be desirable, therefore, to provide a method of making multicomponent molded articles which uses relatively inexpensive, less complex, replaceable and disposable flow distributors, which are relatively easy to machine, clean, and inspect.
U.S. Pat. No. 5,162,074 to Hills teaches a method and apparatus for making multicomponent fibers which uses a relatively inexpensive and less complex flow distributor made up of one or more thin, metal plates etched with distribution flow passages. The use of such a thin plate flow distributor in the spinning method and apparatus disclosed in Hills permits a wide variety of plural-component fiber configurations to be extruded at relatively low cost, with a high density of spinning orifices, and with a high degree of fiber uniformity. Hills teaches that various features must be considered in devising a practical spinning method, including high productivity (i.e., grams of polymer per minute per square centimeter of spinneret surface area), fiber uniformity (i.e., density and shape), and the particular polymers used (i.e., suitability for melt spinning and solution spinning processes). Hills teaches that the only polymers useful therein are those which can undergo melt spinning or solution spinning.
However, Hills does not teach a method or apparatus for making molded articles, including films or parts. In fact, Hills does not even remotely describe molded articles or methods of making molded articles. Hills is only concerned with making fibers. The fluid dynamics involved in fiber-making processes, including spinning and drawing, as in Hills differs from that involved in forming molded articles.
A primary object of this invention is to provide a method for making non-fiber, multicomponent molded articles from a plurality of respectively dissimilar fluid components wherein the method uses a relatively inexpensive disposable flow distributor which is relatively easy to machine, clean, inspect, and re-use.
Another object of this invention is to provide a method for making non-fiber, multicomponent molded articles from a plurality of respective dissimilar fluid components, wherein the method uses a relatively inexpensive, disposable flow distributor which is relatively easy to machine, clean, inspect, and re-use and which is capable of distributing and combining the plurality of components in such a manner as to cause a non-fiber, multicomponent molded article formed therefrom to contain a plurality of components positioned in a predetermined spatial, non-laminate configuration with respect to each other.
A further object of this invention is to provide a structure for making a non-fiber molded article from a plurality of respectively dissimilar components, wherein the structure uses a flow distributor having the characteristics set forth in the preceding objects.
These and other objects which are achieved according to the present invention can be discerned from the following description.